1. Field of the Invention
The present invention relates to an auto-focus system, and more specifically, to an auto-focus system in which a range of an AF area to be set as auto-focus coverage can be changed within a shooting screen.
2. Related Art
As an auto-focus (AF) adopted for a video camera such as a broadcasting TV camera, Contrast type AF is known. The Contrast type AF obtains an image of an object imaged through a picture-taking lens by an image pickup device and controls a focus of the picture-taking lens to maximize a contrast of the image of the object.
The Contrast type AF does not make the entire shooting screen (a shot area) AF coverage. The Contrast type AF usually makes a part, for example a rectangle area, of shooting screen (an AF area) AF coverage. The Contrast type AF in which a range of an AF area within a shooting screen (e.g., the location) can be changed and a desired object in the shot area can be focused by AF has also been known (for example, see Japanese Patent Application Laid Open No. 10-173980).
A video camera has a display (monitor) generally called “view finder”, which displays, for example, an image currently taken by the camera in real time so that an operator such as a cameraperson can check a composition of the image. The view finder is also used as a monitor for displaying various types of information such as information of camera setting or lens setting in addition to the currently taken picture. A view finder in which an AF frame indicating a range of the abovementioned AF area is superimposed on the taken picture is also known.
A video camera whose view finder displays an AF area and a video camera which adopts a line of vision AF mode in which the location of an AF area is changed by the cameraperson's line of vision are disclosed in Japanese Patent Application Laid Open No. 7-283993. With this technique, an indication of the location of the AF area is changed on the view finder in response to a change of the location of the AF area. In Japanese Patent Application Laid Open No. 7-283993, a mode in which the location of the AF area is not changed (central emphasis AF mode) can also be selected as well as the line of vision mode. In such a central emphasis mode, an AF area is not indicated so as to avoid complicating a screen of the view finder.